Showing Interest in the Undergrad Program

Many discussion here and other sites discuss about how the student has to show interest in the programs he is planning to apply.
Would appreciate feedback on what are the best ways to do this (other than personal visits)?

Some places talk about Interview request - would like to know with whom? what should be the questions by the student? What are the typical questions the students should ask to show interest at the same time not look desperate?
Does Skype with video more effective than just a phone call?
Thank you.